Abstract

This article presents a cryptographic key protection technique from physical security attacks through Si-backside of IC chip. Flip-chip packaging leads to a serious security hole that allows emerging backside physical security attacks. The proposed backside buried metal (BBM) structure forming a meander wire pattern on the Si-backside detects unexpected disconnection of the meander and warns the malicious attempts to expose a vulnerable Si substrate. Moreover, the BBM meander also shields key information of cryptographic circuit from both passive side-channel attacks and active laser fault injection as well. Unlike other conventional laminate-based protection, this backside monolithic approach does not require frontside wiring resources or additional packaging layers, resulting in only 0.0025% size-overhead. The BBM meander was formed on the backside of a 0.13- $\mu \text{m}$ CMOS cryptographic chip by wafer-level via-last BBM processing.

Highlights

  • W ITH the rapid growth of Internet of Things (IoTs) applications and devices, data security has been a major issue since IoT edge devices acquire confidential and privacy information and export it to the cloud network

  • It shows that the backside buried metal (BBM) meander and the through Si vias (TSVs) to frontend circuits are seamlessly formed

  • Since the BBM and TSVs are formed in the existing backside Si-substrate and under IO pads, respectively, our technique only requires the additional area of the disconnection detector circuit with extremely small size of 300 μm2, which is only 0.0025% of total chip area on the frontside

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Summary

INTRODUCTION

W ITH the rapid growth of Internet of Things (IoTs) applications and devices, data security has been a major issue since IoT edge devices acquire confidential and privacy information and export it to the cloud network. These attacks target an IC chip rather than signal wiring on-board because it is necessary for attackers to extract a cryptographic key in order to steal or tamper with data instead of destroying it. The active topmetal shield technique can be used for backside protection by bonding two dies back-to-back [8] and, a breakable die with an exotic film lamination structure impedes backside physical attacks [9] They require additional die or layer, which causes an increase in the size of an IC chip.

Si-BACKSIDE SECURITY ATTACKS
PROTECTION CIRCUITS AGAINST Si-BACKSIDE PHYSICAL SECURITY ATTACKS
BBM Structure
Backside Exposure Attack Detection
Backside SCA Resistance
Backside LFI Resistance
CIRCUIT IMPLEMENTATION
EXPERIMENTAL RESULTS
CONCLUSION
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